Fluophosphate glass



Sept. 13, 1949. KuAN-HAN SUN 4E1' Al.

FLUOPHO SPHATE GLAS S 2 Sheets-Sheet 1 Filed Jan. 29, 1946 .y WAM ,MM

FIGZ.

KUAN-HAN SUN AURTCEL.HUGGINS 'l INVENTORS BY m,

A TTORNE Y Sept l3, 1949- KuAN-HAN suN ETAL 2,481,700

FLUOPHOSPHATE GLASS Filed Jan. 29, 194e 2 sheets-sheet 2 A TTORNE Y Patented Sept. 13, 1949 4UNI'T1210(iS-rfrES 2,481,100 PATENT' OFFICE FLUoPHosPHA'rE GLASS Knaur-Han Sun and Maurice L. HugginsQRochester, N. Y., assgnors to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey Application January 29, 194s, serial Nolsiaivs The present invention relates to novel lglasses 'and glass batches from which they are made and,

atomic ratio F/P is above 0.23 and in most cases beloW.2.9, the. fluoride being in many instances, but not-necessarily, introduced partially or entirely as van alkali metal iluoride and in most cases containing other metallic components besides those mentioned The phosphate is the glass former, and' we'preferablyuse the'beryl- -lium and aluminum phosphates, resulting in high lAbbe values. For practical considerations, we 20 have usedY aluminum metaand ortho-phosphates and beryllium meta-phosphate in most cases.

While it is known that iluoride in small amounts may be present in phosphate glass, su-ch glasses with relatively large proportions of fluorine with 25. respect to phosphorus have not been known.

Such glasses have very high Abbe values, in most cases over 70, abnormally high blue partial dispersionratios, and` abnormally low lred partial dispersion ratios. Moreover, they 'have a low melting temperature, thereby decreasing the potential volatilization loss. c

The general systems of iiuophosphate glasses -herein disclosed are: AF-Al(PO3)3; AF-AlPOl;

AF-'MF-n-Be(PO3):l; where A represents one vor more of lithium, sodium, or potassium, and MF1 represents one or more of 4the following fluorides: MgFc, CaFz, SrFz, Bale, ZnFz, LaFa', and ThF4. As disclosed in our pending application, Serial No. 568,314, ledDecember 15, ...1944.813455 may be formed by introducing phosphates in limited amount in a uoride glass, the resulting glass being still essentially a fluoride glass and having the optical properties identiiled with such glass. In all of the examples given in that application 7 Claims. (Cl. 10S-47) 2 the ionic percentage ofuorine was in most cases aboveO, the minimum being 48.34.

The present glasses are in general characterized by being essentially phosphate, an ionic percentage of iiuorine much less than in those eX- amples, an F/P ratio between .23 and 2.9, a low meltlng'temperature, an D value between 1.45 and 1.55, and anAbbe value above 70. The low melting temperature, below 850 C. for mostlof 10 the examples given, and not over 1100 C. for any of them', is an important feature in that it cuts down the potential volatilization loss of gaseous components in nuo-phosphate melts.

We will rstshow thevv ranges of proportions lx1-which some of the glasses having the characteristics mentionedv may be found and thengive Vnumerous specific examples Within those ranges, as well as other examples of other systems,within 'the scope of the claims. l

The first table, I,. gives vthe proportions by weight and mole for several binary systems, each consisting of an alkalimetal iiuoride and a phosphate of aluminum or beryllium. 'lhe'r'arlgeof proportions of the alkali metal fluoride and the ratio of the number of atoms of fluo-rine to the number of atoms of phosphorus are given. f

Table I Systems F P Wt. Per Mole l Gent Per Cent LiF-AHPOm 2li-39Y 76-87 "1214212 NaF-AMPOx); 24-41 66-81 0.7-1.4 (P 32-46 68-79 0. 7l. 3 26-31 62-68 l. 6-2. 1 20-36 42-.62 0.'7-1'. 6 31-36 4953 l. 0,1'. l 10-39 32-81 0. 23-2. l 10-50 32-80 .2B-2.0 40 `.KF-BeCEOQz. 1li-54 :S2-77- .2S-1.7

. .In the next table.. showing the ran-ges of proportions of the components of certain ternary systems, AF represents lithium or' sodium uoride; MFz represents the uoride of magnesium, calcium, strontium, barium, or zin'cg.. and R(POa)y represents A1(PO3)3 or Be(PO3)2.

SystemsV BEB/blst Weight Mole Weight Mole` 'Weight Molem Per Cent Per Cent Per Cent Per Cent Per Cent Per Cent LiF-MgFz-AMPOm 13-39 46-87 0-29 0-37 56-76 l7-24 2. 3 LiF-CaFq-AMPOsls"- 8-39 29-87 0-39 0-48 46-76 13-24 2.9 LiF-SrFz-AKPOQM. 12-39 4787 0-48 (Hi8 40-76 15-24 2. 7 LiF-BaFz-A1(P0a)a 8-39 42-87 0-58 0-42 33-76 13-28 `2. 6 LiF-ZnFz-AKP 0:)3. 12-39 48-87 0-38 0-34 50-76 18-24 2. 2 NaF-Ca'Fr-AKP 093.-.; 25-41 55-81 0-23 0.27 52-76 18-34 2. 0 LiF-'CaFr-Be(1?0a)z 15-39 45-81 0-3() 0-30 V55-9() 19-74 2. 1 LiFSrF2-Be(POa)z 13-39 46-81 0-35 0-26 52-90 l 19-74 2. l LiF-BaFq-BeUOm 10-39 42-81 0.40 ,0-26 50-90 19-74 2.1

l Table VVI In lthese examples, mixtures of. uorides of divalent metals are given, and in general, for reasons elsewhere pointed out, these are preferable over the simpler formulas.

ting

in each cent on In the following tables of batch. compositions the Weight per cent of each ingredient is case given on the left'l and the mole per the right. Table III gives examples oonss .one and/or phosphates of other elements than glasses have optical values in 'fields not hitherto 'Table VIII j' Example vnr-1 'Weight Mole 5 er'Cent Per Cent 4 r9.1 5 14. 8 Magnesium 'tluorid 2 l 4:0 Calcium fluoride.- f 5 9.6 m .strontium iiuoride- 14.8 Barium fluoride 14. 2 Lanthamnn fluoride (LaFs), .3:8 AMPOM 42 19.8

m" W' it@ 15 n i jLD. 74.0

Although in all .of the examples above given 9,481 ,roe

available. Area B "ll icates the region for @the most common comercial glasses; C, the'rare' lelement `berate glasses'disclosed in Morey Reissue Patent 21,175; D, fluoride glasses. It is to he under-stood that these areas are approximate only and are not .as sharply ydefined as kthese boundary lines would seem to imply. A indicates approximately the area within which these values fall ferr fluophosphate glasses.

'The values of nn yand v are given above, where known, for each formula; and in addition ce1-tain other optical properties of some of the examples are given in Tables X and XI. Table X gives the dispersion between certa-ln lines of the spectrum, and Table XI gives the partial dispersion ratios between certain lines; for two wave lengths,v M and M,

alkali metal fluoride is present, usually in considl www erable amount, and the phosphate vincluded in'20 'L Fnv rauen nF-w nm-m nvr-n, 7n.-m vnie-'lm vnr-nc nps-ny the batch is of either beryllium'or aluminum, we 'consider as includedin the scope of our inventions glasses made from batches containing only iluorides of metals having a higher 4valence than 40 beryllium and aluminum. `Examples of these will now be given. In Table IX are included examples containing no alkali metal fluoride. The data yfgiven in parentheses are equivalent to those elsewhere given.l y L 45 Table IX Lx-i 1X-2 g IX-a 1X4 iw Mlw` M: w `M '50 I to It is well known that glasses cannot be formed in all proportions of the ingredients; and to illus- -for the .correspondingly numbered glasses.

Table XI Sample No A n, i vl1 r wn :vacv um'.

IV-l (1). 431 0.522 0.698 V .536 106 V 437 ,531 703 V 43.9 l .533 d I' V 437 .530 200 V 444 .'541 .703 `V 440 l 531 i ..703 V 442 .537 7.04 v A532 .702- l v1 ,-441 539: 703

V1 442; ..536 .702; v1 .441 .541 .703 VIH-l u A43 539 ..793

The novelty of these optical properties is more clearly shown in Figures 3 and 4. In these iig-- ures the :dash lines passing through regions and M indicate .the general: axis of grvs. v, and um', v, respectively;for4 typical well known `comr-nercial glasses, indicated individually by x;

and the .numbered small Vcircles in areas N and N ',respectively show the positions oi these values It to be understood that vm', is equal to 'the sum of vrD .and una.

In Figures `fi and 4 the positions oi these values for fluoride glasses are indicated 'by small triangles 'in areas P and P., respectively. The limits of these areas are not exact and are not indifcated except as they are to he inferred from the data as given.

Although our illustrative examples are predominantly simple systems, it is-Well known that the .introduction of small amounts of various compatible ingredients or constituents usually ,helps to prevent devitrication or other phase separar tion and to increasethe chemical durability of the glass. I ikewisersomeV ofv the4 calcium content may be replaced 'by a corresponding amount,

.assi-m9 atom-for atom,-of @chemically similar*V element BeFz.Ba.O.P205

or BeO.5BaO.4-PzO5.2PF5 or in other ways. To

' make a beryllium,bariui'rlruophosphate glass one may heat together' appropriate amounts of (NH4)2BeF4 and Ba(PO3)2,for of BaFz and Be(PO3) z, etc. strict our claims-to any particular combination .of compounds originally used in thebatch, as

For these reasonswedo not.re,....

these chemical equivalents may be used; and the.

claims are tobe interpreted as including such equivalents.

vessels may be safely usedif there are no organic substances, reducing agents, or compounds con-v taining boron presenti,` Since most of these In melting these glasses, the'raw materials should contain no wateror moisture. Platinumv C., they can also be melted in a pure silvervessel if due precautions are observed. The batch should be mixed thoroughly. The time of melting depends on the compositionfthe size-of the melt, and the temperature applied.v It varies from about 5 to about 100 minutes for meltsof 20 to 1000 grams,V at about 850 C. The melted liquids are usually yellowish-in color and rather huid.V VThe uidity Varies slightly with the alkali metal content. The higher the alkali metal content, the more fluid the liquid. A cover for the melting vessel is necessary in order to cut down- -the volatilization of vapors.

Volatilization loss is a functionof composition, temperature,l and heating time. Our success of melting Vthese glasses is a result of our realization ofA the .fact

that they can be melted inosuch a low tempera-9' 'ture region. For each glass composition it is important that the` optimum temper atureV range should be used, and the time at the-higher tem- "peraturesshould be madeY as small as possible, in order to cut down thervolatilization loss. Uri-5'1" der careful control, thejtotal volatilization loss' is -rather small (about l5 per cent'of the'totalweight lof thejmelt) and ,the evect of volatilization on the optical properties is also small, as evidenced corded as followsrffionelfkilogram of the batchy of. ExampleA VI-5 Was` mixed and fed into a coveredplatinum beaker of about 500 cc. capacity inafurnace with apparent temperature about 920 C'. It took about one and one-half hours to feed all the batch in and to obtain a iiuid liquid. The liquid wasA heatedfor about one-half( hour toallow complete solution of all ingref Y dients.v :The furnace vtemperature was thenjlow- 'ered to about 800 C. and the liquid was stirred vwith ai motor-driven platinum stirrer '-for'a Vfew V'minutes` The liquid was then poured into a mold which, at the time of pouring, was at a tempera"- "ture f about 300 C. A clear glass resulted after coolingdown slowly in the molding'oven., n

Although most -of the examples hereinv given include `alkali metal-fluoride andY have -an -lF/P ratio not greater than 2.9, it is to be understood 'that we Y`consider as within the scope of,` our in,- vention iiuophosphate glasses .without alkali metal, as instanced in [Table IX. Other examples within the scope of our invention are to be found f anapplication, Serial No. 644,179 filed concur'- Y rently by Kuan-Han Sun, one of the presentr inventors, who is the sole inventor and discoverer of. the subject matter therein disclosed and -specically claimed. Certain of the examples therein given have anF/P ratio greater than'2.9 anda value of 11D Vgreater than 1.55, within the .area A shown in Figure 2. u Y

Having thus described our invention, what We claim is:

1. A fluophosphate optical glass consisting of l the 'fused heat reaction product of a batch including by weight: lithium fluoride, 8 to 39 per cent; calcium fluoride, 0 to. 39.per. cent V'and an aluminum phosphate, A40I to 76ffper `cent,rthe.

atomi-c proportion vof fluorin'e tophosphorusb'eing' between 0.23 and 2.9, the'remainder beingfjcorfripatible material. l f .Y VA

2. A fluophosphate optical glass consistingff thefused heat reaction product of "a batch includlng by molecular, prolfiortionsj;V lithium nupriqe, 29` te 8 7 per cent; calciumjnuondegzjs to` 35 percent; barium fluoride, 12.5 to '20z percent; and an aluminum phosphate, 17515025 per cent; said four compounds totaling at least 75 per cent VAof the hatchand having'an atomic proportion *of fluorine to phosphorus between 1.0 and 2.9.

'3. A' lu'opho'sphate optical glass consisting of the fused heat reaction product of a batchY including: alkali metal fluoride chosenfrmthe group consisting 'of the fluorides `,of lithium,

.sodium, and potassium, 8 to 3,0 per cent by weight; .55.

vthe iiuorides` of magnesium, calcium, strontium,

and barium totalingV from 30 to 50 per cent by by the unusually high'Abbe values of these* glasses. After melting toa clear` liquid, the'tem perature may be loweredabout 150 C., and the liquid may be stirred by a platinum or silver stirrer drivenby a motor. The liquid isV `then poured to a mold at a temperature range20G-330o C. The optimum molding temperature (like, the optimum melting temperature) is'a function of the amount of alkali metal uoride present. The

high alkalil-metal-containing glasses haveboth 10W melting vand lowV molding temperatures.

Most of these glasses arev durableto moisture attack, with the exception of a few that contain very high alkali metal fluorides. u v v The melting of' atypical batch maybe reand 1.55.

40,110;V 62 perj-cent by weight, andV having an'4 nD value between 1.50 and 1. 55and an Abb e value greateri?l'1.?tn,70.0,..H `4. A fluophosphate optical glass `consisting of thej fused heat reaction product Vof a batch including lby v molecular proportions: lithium iiuorideyl9fto50per cent; calcium fluoride,V 9 to 35`per cent; bariumiiuoride, 1 to' 20 per cent; and Valuminum metaphosphate, 17 to V25 per cent, said glass'h'aving'a refractive index between 1.45

' 5. An optical uophosphate'glas's consistingof the fused heat reactionr product lof abatch consisting by weight of': alkali metal uoridechosen "fro'm' the group consisting of the fluorides ofr lithium, sodium, and potassium', 7 to 30 per cent; iluoride' chosen 'from the group consisting ,ofthe iiuorides'of magnesium, calcium, zinc,.strontium.

and barium, 20 to 52 per cent; and an aluminum phosphate totaling 37 to 65 per cent; said glass having an nD Value between 1.45 and 1.55 and an Abbe value greater than '70.0.

6. A iluophosphate optical glass vconsisting of the fused heat reaction product of a batch including by molecular proportions as essential and predominating ingredients: alkali metal uoride chosen from the group consisting of the iiuorides of lithium, sodium, and potassium, 33 to 76 per cent; uoride chosen from the group consisting of the uorides of magnesium, calcium, zinc, strontium, and barium, 8 to 47 per cent; and aluminum metaphosphate, 16 to 24 per cent, the atomic ratio of fluorine to phosphorus being between 0.23 and 2.9.

7. An optical uophosphate glass consisting of the system AF-MFz-R, where AF indicates fluoride selected from the group consisting of the fluorides of lithium, potassium, and sodium,

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date Drakenfeld May 13, 1919 

